Acoustical material



March 12, 1935e H. T. coss ACOUSTICAL lMATERIAL File-d Aug. 18, 1951 auf.

INVENTOR lrwrold T. C056.

ATTORNEY Patented Mar. 12, 1935A UNITED STATES PATENT oFFllcl:

ACOUSTICAL MATERIAL Harold T. Coss, Somerville, N. J., assignor to Johns-Manville Corporation, New York, N. Y., a corporation of New York Application' August 18, 1931, Serial No. 557,851

13 Claims. (Cl. 'l2-17) This invention relates to an acoustical material. A mixture is formed of a combination of plas- More particularly, it relates to adecorative, washtic clay, a quick-setting cementitious material, able, and permanent sound-absorbing article as for instance, a hydraulic cement such as plascomprising patches of non-permeable material ter of Paris, sawdust, and chemicals which refirmly adhering to the surface of a permeable act in the presence of water and acid to form 5 sound-absorptive base, and the process of making carbon dioxide gas. This mixture is then added the same, to water and acid, with rapid stirring, until uni- Materials to be used for the absorption of formly vwetted to a plastic slip condition, and sound should be permeable. 'This implies the is cast into molds coated with water-repellent presence in the sound-absorbing material of pores material. The mass rises like dough within about 10 which are intercommunicating and which termi- 5 minutes from the time of wetting, and sets in nate in openings at the surface, to give a pitted about 10 minutes, so that the sides of the conappearance. y taining molds may be removed. The bloated I have now discovered means of making an mass is then handled on pallets into a dryer,

attractive tessellatedrsurface of an acoustical dried, set in a kiln, and fired to the maturing l5 article. Briefly, I have discovered that I may temperature of the clay until a ceramic bond is apply, over a substantial area of the face or surproduced. During the firing, the sawdust is deface of a permeable sound-absorbing base macomposed with the production of gases'which, in terial, rmlyadhering patches of ceramic glaze escaping, produce channels that provide interor other non-permeable material, without decommunication between the interior of the prod- V2() creasing greatly the sound-absorption andwith uct and the face and other exterior surfaces the production of a decorative, washable and thereof and also between the gas cells produced permanent surface. originally by the formation of the carbon di- The following example illustrates one method oxide gas. After cooling, -the product may be of practicing my invention. Over the surface of sawed or ground to any shape desired. An ex- 25 a permeable base there is applied, in small areas ample of the specific proportions which may be or patches, a composition adapted to develop a used follows.

ceramic glaze and a vitreous surface and to form Parts a discontinuous surface that is suitably elevated Dry materials by weight with respect to the surface of the permeable. Flint re clay 600 30 base. The whole is then fired, to develop a Plastic retort clay 550 ceramic bond and make a durable article Vwith Siliceous filler clay 550 patches of firmly adhering glaze. As the per- Plaster of Paris 250 meable base, there is preferably employed a Whiting (through 60 mesh) 80 ceramic material with inter-communicating pores. Alum(paper makers aluminum sulfate) 80 35 ending in openings at the surface. Sawdust (through 20 mesh) 400 c In general the sound-absorptive base material employed is preferably rigid instructure and is W te 170 permeable in an directions, that is the pores conuf r. 23 4 i0 tained therein extend both laterally and vertis une a'ld" concentrated callyY with respect to the face exposed to the In addition to the above product, permeable, sound to be absorbed and terminate in openings ceramic material which may be employed as the' in the plane of the exposed face. The base mabase material in accordance with my invention terial is preferably ceramic and the invention may be produced by various othermethods.

hereinafter is specically describedinconnection The invention is further illustrated by the 45 with such a material. However, other types of drawings of Figs. 1,v 2 and 3. Fig. 1 is a plan permeable sound-absorptive material, particuview of the product, Fig.. 2 a corresponding side larly those of a rigid stone-like character which elevation, and Fig. 3 an enlarged .side elevation depend upon their permeable structure rather of the base material. 1

than inherent resiliency for their absorption In Figs. 1 and 2, there are'evident the regu- 50 effectiveness, may be substituted. larly shaped patches 1 over the surface of the A permeable ceramic material which has been permeable base material 2 and also the surface made with excellent results in accordanceV with pits or pores'in the permeable base. In many of my invention was'produced according to the fol'- these larger pores are dots 3 indicating small lowing procedurezcapillary channels or tubes which provide com- 55 Wet materialsmunication with other pores inwardly disposed.

Fig. 3 is an enlarged side view of the soundabsorption base showing not only that many of the large pores have perforations 3 (indicated by dots) providing inner communication but also that the pores sometimes communicate with laterally adjacent ones, as indicatedby the union of some ofthe more or less circular lines bounding individual pores.

Since the capillaries or other means connecting the cells extend into the article both vertical- .ly and laterally to the surface exposed to the sound, these connections provide means whereby sound striking the permeable surface adjacent to an impermeable patch may penetrate the sound-absorbent material behindthe patch.

An illustrative method of producing a typical, complete article is described in detail below.

Over a planed and well cleaned surface of a permeable ceramic base made, for example, as described above there is laid a stencil, suitably provided with a plurality of small open spaces adjacent to one another. Through the stencil openings, there is then painted or sprayed an engobe, compounded to firmly adhere to the porous base, on the one side, and to the glaze later to be applied, on the other. The engobe is smoothed and isthen sprayed or painted over with a glaze composition. 'Ihe stencil is removed and the glaze composition surface is dampened slightly with water, as with a sponge, brush, spray, or other suitable means, and pressed slightly, as with a dry cloth or felt roller, to flatten down any corners or edges which may have been lifted slightly in removing the stencil. The article is then dried and red to vitrify the glaze and ceramically bond it and the engobe to the base.

By using this procedure, with stencils designed to give attractively patterned or regularly shaped small, discontinuous patches of the tile or glazed surface on the permeable base, there have been produced surfaces of attractive appearance. At a short distance the glazed tile patches with the intervening areas of base material give the appearance'of a mosaic. At greater distances, with highly colored tile constituting the glazed patches, the surface appears almost as a solid glazed surface. l

In the procedure outlined above, various engobes may be used, as for example,` one of the following composition: Cornwall stone 43% by weight, feldspar 20%, china'clay 13%, and ball' engobe is so applied as to fill hlesk and irregu-l larities of the exposed parts of the permeable base and to make a rm, opaque, and smooth base, like a pottery body, to which the glaze is then applied. The glaze is then sprayed, dipped, or painted over the engobe while the stencil is still in place.

The glaze used may be any one of a number of I types, of which the following two `compositions The mix- One of these glazes is ladapted to give a glossy surface after firing; the other, a matte surface.

Composition of glaze, parts by weight Material Glossy Matte In addition to these two` opaque glazes, colors were obtained by introducing and grinding into the batch coloring oxides, as, for example, 2% of copper oxide on the weight of the formula for producing a glossy surface. In an oxidizing fire, this gave a brilliant green shade. With the matte formula there was incorporated, in one preparation, 0.18% cobalt oxide to produce a blue glaze after ring. It will be understood that the intensity of the color of the glaze varies with the thickness of glaze coat applied, as well as with the proportion of pigment added to the glaze composition. Also it .will be understood that there may be incorporated other pigments or coloring materials used in the making of colored glazes or ceramic articles. For example, there has been used a complete set of Professor Charles F. Binns matte colors and twenty principal majolica colors. These indicate the wide variety of shades which it is possible to produce After application of the engobe and glaze, the' drying may be done at a usual rate. Or, the drying may be omitted as aseparate operation and the tile fired immediately. With the formulas tabulated above, there has been used for firing, a clean oxidizing atmosphere, especially during the soaking period, and a maturing temperature of 1750 to 1900 degrees F., suitably 1800 degrees F. A11 exception was made with the colors of Professor Binns, in which case a. maturing temperature of approximately 2000 degrees F. was used. Before ring, the tiles are suitably set on edge. After firing, the rate of cooling should be suiiciently slow to avoid crazing. A total time of cooling of 9 hours before opening the firing kiln has been used.

Since the glazed patches constitute an attractive feature of kthe appearance of the finished article, the pattern may be selected to leave the largest amount of exposed base material for sound-absorption with a minimum of conspicuousness of such basejmaterial. A pattern which is satisfactory for this purpose is a modified basket weave in which the patches are in the form of small squares or of rectangles' each of an area of the order of four-hundredths of a square inch, uniformly spaced over the surface and covering 52% of the total surface. While this pattern leaves exposed only 48% of the surface of the permeable base, it has been discovered that it does not decrease greatly the sound-absorption efficiency through that surface. The following data show the effect on the absorption of incident sound by typical specimens, as measured bythe reverberation method, when the surface exposed to the sound is partly glazed in this manner, and, forcomparison, the sound-absorption when such surface is not glazed and the permeable base is completely exposed.

Percentage of sound absorbed Character of surface exposed to sound Frequency Frequency 250 to 500 to 1,000

cycles cycles Surface with patches of glaze covering 52% of the total area 39% 57% Surface with no patches 43% 60% The decrease in sound-absorption, in the two cases, is 4 and 3 units, respectively, or less than one-tenth or 10% in each case. It is evident, therefore, that the surface constituted of the patches and intervening areas of sound-permeable base material is adapted to admit a large proportion, say at least '15 per cent of the sound incident upon that surface. I

Many variations from the details of the examples given for the purpose. of illustration may be made without departing from the spirit of the invention. Thus the size of the individual patches or areas applied over the permeable base may be varied considerably, either to alter the appearance, for architectural purposes, or to change the properties, for absorbing sounds of different frequencies or pitches. Thus the area of the individual patch may b e 0.01 to 0.04 square inches, 0.04 to 0.10 square inches, or 0.10 to 0.30 or 1 square inch, the exact size depending upon the effects which it is desired to produce and the character of the sound-absorptive base. I have used to advantage spaced, discontinuous patches of individual area equal to 0.04 square inch for producing a desirable appearance and permitting satisfactory absorption of sound of medium pitch.

The patches may be irregular in shape, such as produced by spraying a more or less lumpy paste discontinuously over a surface. However, the effect produced with regularly shaped patches of the glaze,.such as squares, rectangles, stars or apparently woven patterns, is particularly pleasing.

Units of acoustical material made in accordance A with this invention and having each different patterns or colors may be used in a` structural assembly, as, for example, in a ceiling or wall, to give various pleasing effects.l

The percentage of total area of the permeable base which may be covered with the nonpermeable glaze or smooth surface may likewise be varied in accordance with the appearance desired, or the quality or percentage of the sound to be absorbed. In general the area covered in any particular instance is a compromise between these two factors. In most instances the covered area 4will constitute not less' than 10% and not more than 85% of the exposed surface and a still more closely confined range of 25-70% or LO-60% le. g. 52% as specifically described above is desirable. Preferably, the size, shape, and arrangement of the covering patches are such that the sound-absorption through the surface having the patches upon it is decreased by not more than one-fourth or 25% and preferably less than 10% from what the absorption would be if the permeable surface were entirely uncovered.

The glazed tile or patches may be substitutedpatches of rough or uneven surface, I have found satisfactory the smoothing of the patches to an even surface that is' elevated with respect to the surface of the permeable base. Patches such as those of plaster or cement may be colored by the inclusion of pigments or by painting or lacquering thesurfaces. y v' If a different effect is desired, the engobe and/or glaze composition may be used in such quantity and in such manner as to coat more or less uniformly the high spots of the surface of the permeable base. For example, one face of a permeable ceramic base may be dipped, without theuse of a stencil, in an engobe and then in a glaze composition and fired. In this process, the proportion of water to dry materials in the engobe and glaze compositions is suitably quite large, to give a relatively fluid mixture that will not bridge over or close a greater area of the surface openings of the pores in the permeable base than above indicated.

The terms permeable and non-permeable as used in the specifications and claims referto the absorption of sound by the material. Thus a permeable material is one which is adapted to admit and absorb sound waves, whereas a nonpermeable `material is not so adapted. Permeability is indicated also by the ready passage of air, under slight pressure, through the material. Materials of 'wide range of quality or soundabsorption or permeability may be used as the base. 'Ihus, there may be used baseslwhich, in one-inch thickness, absorb -to 80% or more, suitably 40 to 60% of sound of 512 cycles frequency. When the base with its applied patches of smooth material is not to be fired, arpermeable block of non-refractory material, as, for example, plaster, may be used as the base.

In place of applying a glazable material to the ceramic base material, the base material may be fired in such a manner as to partially glazel the surface e. g., by ring inthe presence of volatile fluxes such as sodium chloride, and ring so that the surface is not entirely glazed but v itried only in scattered patches, thereby providing alternating patches of permeable and non-permeable surface, or so that the surface is glazed substantially completely over the high spots, to leave open a number of pores communicating with lnner pores. Suitably at least half the total area of surface pores are left in approximately the same state of communication with the interior as before the glazing. r Inone process of making such a glaze, salt may lie-introduced in limited quantity into the 'nre-box of the kiln in which the permeable base is being flred.

A modification of 'the invention that may lower the cost of production or increase the utility of v treated face is dipped into the engobe and then into the glaze composition in such manner that only the high spots or plateaus are coated, the channels or low areas being left uncoated. The

5 product is then fired to vitrify the patches of glaze and ceramically bond them to the permeable base.

The terms permeable and non-permeable, as used herein, refer to the permeability or nonpermeability to air-borne sound.

The details that have been given are for the purpose of illustration, not restriction, and variations Within the spirit of the invention are intended to be included in the scope of the claims.

What I claim is:

1. A sound absorbing article comprising a sound-absorptive base material having cellular spaces that communicate in directions lateral and vertical to the surface exposed to the sound to be absorbed and patches of impermeable material firmly adhering to the said surface.

2. A sound-absorbing article comprising a sound-absorptive rigid base material having ce1- lular spaces that communicate in directions lateral and vertical to the surface exposed to the sound to be absorbed and patches of impermeable material firmly adhering to the said surface.

3. An acoustical tile comprising a base of porous, rigid, sound-absorbing material permeable in all directions, the surface of the base exposed to the impingement of sound being composed of alternating areas of non-permeable and permeable material, the non-permeable area constituting not less than 10% and not more than` 85% of the total exposed area.

. 4. An acoustical tile comprising a base of porous, rigid, sound-absorbing ceramic material permeable in fall directions, the surface of the base exposed to the impingement of sound being composed of alternating areas of non-permeable and permeable material, the non-permeable area constituting not less than 10% and not more than 85% cf the total exposed area and being substantially uniformly spaced thereover.

5. A sound-absorbingarticle comprising a sound absorptive base ceramic material having cellular spaces that communicate in directions lateral and vertical to the surface exposed to the sound to be absorbed and patches of impermeable ceramic material firmly adhering to the said surface.

6. A sound-absorbing article comprising a permeable ceramic base provided with intercommunicating pores adapted to absorb incidentv sound and communicating with the face of the article and firmly adhering non-permeable patches of ceramic material covering approximately half of the face of said base exposed to the sound to be absorbed.

7. A sound-absorbing article comprising a permeable ceramic base provided with intercommunicating pores adapted to absorb incident sound and communicating with the face of the article and firmly adhering non-permeable patches of ceramic material coveringless than per cent of the face of `said base exposed to the sound to be absorbed.

8. A sound-absorbing article comprising a permeable ceramic base provided with intercommunicating pores adapted to absorb incident sound and communicating with the face of the article and firmly adhering non-permeable patches of ceramic material covering a substantial part of the surface of the base exposed to the sound to be absorbed, the said patches having individually an area of the order of four-hundredths of one square inch.

9. A sound-absorbing article comprising a permeable ceramic base provided with intercommunicating pores adapted to absorb incident sound and communicating with the face of the article and `firmly adhering non-permeable patches of ceramic material, said patches having individually an area of approximately fourhundredths to one-tenth of one square inch and collectively an area equal to approximately half of the surface over which they are applied..

10. A decorative acoustical material comprising a permeable base provided with intercommunicating pores adapted to absorb incident sound and communicating with the face of the article and regularly shaped patches of smooth outer surface firmly adhered to the base, said patches forming a discontinuous surface that is elevated with respect to the surface of the base porous article.

11. A decorative acoustical material comprising a permeable base provided with intercommunicating pores adapted to absorb incident sound and communicating with the face of the article and -regularly shaped patches of smooth outer surface, applied to one face of the base, said patches forming a discontinuous surface that is elevated with respect to the surface of the permeable'base and covering approximately half of the surface to which they are applied.

12. A sound-absorbing article comprising a ceramic base provided with pores communicating With each other and with an outer surface of the article and firmly adhering non-permeable patches of ceramic material covering .substantially less than all of the face of the said base exposed to the sound to be absorbed, the said patches de` ning therebetween exposed areas of sound-permeable material and being elevated above the said areas.

13. A sound-absorbing article comprising abase including a fired clay binder provided with pores communicating with each other and withv the surface of the article and non-permeable patches of ceramic material disposedover and integrally united to a surface of the article.

HAROLD 'I'. coss. 

